ADA Depot - A Forum To Support Users of ADA Amplification Gear

Let's Get Technical => Troubleshooting Problems => Topic started by: DesmoBob on June 29, 2015, 07:43:37 PM

Title: Troubleshooting hum and weird microphonics
Post by: DesmoBob on June 29, 2015, 07:43:37 PM
I made a custom pedal board. I have a 1/4" input jack for the guitar on the right side. The jack is connected via patch cable to the first pedal in the chain.

If I plug my guitar directly into the first pedal in the chain (i.e., bypass the jack on the side), all is well.

However, whenever I use the jack, the patch cable goes loudly microphonic, as do all the other patch cables between the pedals. There is also a loud hum. Do I need to put a filter on the jack? Is the jack itself functioning as some kind of bad buffer? Or is this a symptom of some other problem?

Originally, I had the input jack, plus a wireless receiver. Using a DPDT rocker switch, I could choose which signal (jack or receiver) I could feed into the first pedal. However, any time I switched to the jack input, I got the loud cable microphonics and hum. For now, to make it simple, I completely removed the switch & receiver from the circuit. The point I'm at now is just trying to get the jack to play nicely, period.
Title: Re: Troubleshooting hum and weird microphonics
Post by: Systematic Chaos on June 29, 2015, 09:58:11 PM
I guess the jack is the problem/issue....some grounding or other probably.
For your application I highly recommend these:
http://www.neutrik.com/en/audio/plugs-and-jacks/locking-1/4-chassis-jacks/nj3fp6p-bag (http://www.neutrik.com/en/audio/plugs-and-jacks/locking-1/4-chassis-jacks/nj3fp6p-bag)

(http://www.muziekhandeljoosten.nl/contents/media/l_neutrik%20nj3fp6b.jpg)
Title: Re: Troubleshooting hum and weird microphonics
Post by: rnolan on June 30, 2015, 05:47:30 AM
I'm with SC here, that jack seems to have issues, replace it, make sure you have good "shielded" connection to the first pedal (or just plug straight into the first pedal (for now  >:D )
Title: Re: Troubleshooting hum and weird microphonics
Post by: DesmoBob on June 30, 2015, 12:19:43 PM
Thanks, I'll give that a try. I was able to source the NJ3PF6C, but not the NJ3PF6P (metal housing as opposed to plastic housing). Do you think it would matter?

(Currently I'm using a switchcraft jack.)
Title: Re: Troubleshooting hum and weird microphonics
Post by: Systematic Chaos on June 30, 2015, 10:13:31 PM
The metal one will do just fine..I personally prefer the plastic housing ones for pedalboard/patchbay/rack installation though....
Title: Re: Troubleshooting hum and weird microphonics
Post by: rnolan on July 01, 2015, 05:51:55 AM
Hey SC, do the plastic ones earth to the case ? if not (which is what I suspect) it reduces the possibility of ground loop isses and so would definitely be better, but depends on how you are setting up your pedal board ground plane (there maybe some scenarios where you want everything to earth to the case ?).